Online resets the expiration time for any given key. If key doesnt exists, it
means key (user) become online and should be set as online. Whenever
application gets any probe from a client should call this function. This
method performs way better when there is a throttling mechanism implemented
on top of it, please refer to benchmarks

const (
// Unknown is for errored requestsUnknownStatus = iota// Offline is for displaying user as offline in the systemOffline// do not handle unset variable as offline
// Online is for displaying user as online in the systemOnline
)